This is just a prototype, and we have focused on making it stable rather than covering lots of features poorly. We will be adding new features rapidly — we hope to push new changes live every two weeks or so. To help us prioritize which features to work on when, we’d love your thoughts on our feedback page to help guide our work for you.

In short: the modern mainstream desktop browsers. In terms of which particular browsers it should work in, the recent versions of three of the major four desktop browsers — Google Chrome (23+), Mozilla Firefox (17+) and Apple Safari (6+) — all work fine. Microsoft Internet Explorer is currently black-listed until we can find a way to make it work. Some other browsers also work.

Mobile support is something we're obviously going to include, but right now we haven't tested it properly — feedback would be welcome. We think there should be a serious discussion about which browsers we should and should not support, bearing in mind our limited resources but also our goal in making editing Wikimedia projects as easy and open to all as possible, and we would welcome your input.